The matrix proteins of bones and teeth play key roles in the structure and function of these tissues. Our objective in this investigation is to study the biosynthesis of these macromolecules and to understand the regulation of their expression. The expression of bone and enamel matrix proteins has been studied using RNA from bone cell cultures or ameloblasts and cell free translation. Specific matrix translation products have been successfully identified using polyclonal antisera directed towards each matrix protein. Recombinant cDNA libraries are currently being constructed with the goal of isolating individual genes encoding bone and enamel matrix proteins. These genes will be used to determine the primary structure of these proteins as well as the regulation of their expression during development and disease.